Charge dissipating truck bed and liner

ABSTRACT

A truck bed or liner for installation in a pickup truck bed or cargo vehicle exhibits improved electrical charge dissipating characteristics. The preferred embodiment bed is manufactured of high density polyethylene (HDPE) or similar material containing particles of conductive material such as carbon black dispersed therethrough. In a first alternate embodiment, the bed defines a two-layer composite or sandwich. The upper layer of HDPE or similar material includes dispersed carbon black particles whereas the lower layer is free of such particles. A second alternate embodiment of the invention comprehends a bed liner for disposition in a pickup truck or the like wherein the conductive material is dispersed throughout the liner material. In a third alternate embodiment, the bed liner of the second alternate embodiment is combined with the composite conductive and non-conductive layers of the first alternate embodiment. In a fourth alternate embodiment, a bed or liner of HDPE or similar material includes an open mesh fabric or webbing which has carbon black particles dispersed therein. The mesh or webbing is secured to the upper surface of a liner made of HDPE, preferably by autogenous bonding.

BACKGROUND OF THE INVENTION

The invention relates generally to beds and liners for pickup trucks,cargo vehicles and the like and more particularly to a bed or linerhaving improved electrical charge dissipating characteristics.

Liners for motor vehicles, particularly bed liners for pickup trucks andcargo vans provide many benefits. First of all, such bed liners providea resilient barrier between the cargo area and the actual truck bedwhich absorbs energy and reduces denting and damage to the bed whenheavy loads are transported. Second of all, such liners protect thevehicle bed or interior from water, salt and other possibly morecorrosive materials which may be carried in the vehicle.

The emphasis on passenger car weight reduction has created a similaremphasis on behalf of manufacturers of light and medium duty trucks. Oneof the areas that has become a focus of such weight reduction is thevehicle box or bed. Replacing the metal box or bed with a non-metal,e.g., thermoplastic material, bed provides obvious and relativelysignificant weight reduction and other advantages. Resistance to rustingor corrosion and denting are but two of the accompanying advantages.

A drawback that accompanies relatively large components made fromthermoplastic or other organic materials is their ability to becomeelectrically charged and their inability to quickly dissipate suchcharges. This electrical activity is viewed as undesirable and productswhich do not exhibit this activity would therefore be desirable. Thepresent invention is directed to such a product.

SUMMARY OF THE INVENTION

A truck bed or liner for installation in a pickup truck bed or cargovehicle exhibits improved electrical charge dissipating characteristics.The preferred embodiment truck bed is manufactured of high densitypolyethylene (HDPE) or similar engineered thermoplastic materialcontaining particles of carbon black or other conductive materialdispersed therethrough. In a first alternate embodiment, the bed definesa two layer sandwich. The upper layer of HDPE or similar materialincludes dispersed carbon black particles or other conductive materialwhereas the lower layer is free of such particles. In a second alternateembodiment, a truck bed liner of HDPE or similar material includesdispersed carbon black or other conductive material.

A third alternate embodiment comprehends a truck bed liner defining atwo layer sandwich with carbon black or similar conductive material inthe upper layer. A fourth alternate embodiment bed or bed liner includesan open mesh fabric or webbing which has carbon black or otherconductive material dispersed therein. The mesh or webbing is secured tothe upper surface of a liner made of HDPE, preferably by autogenousbonding. Beds and liners according to the present invention provideimproved dissipation of static electricity charges and thus improvesafety with regard to possible static discharges.

Thus it is an object of the present invention to provide a truck bedfabricated of thermoplastic material containing dispersed particles ofconductive material.

It is a further object of the present invention to provide a highdensity polyethylene (HDPE) truck bed having dispersed conductiveparticles which provides enhanced electrical charge dissipatingcharacteristics.

It is a further object of the present invention to provide a liner for apickup truck or cargo vehicle fabricated of HDPE containing dispersedparticles of conductive material.

It is a still further object of the present invention top provide aliner for a pickup truck or cargo vehicle fabricated of HDPE whichprovides enhanced electrical charge dissipating characteristics.

It is a still further object of the present invention to provide a truckbed or liner comprising two layers of HDPE or similar material, one ofwhich includes dispersed particles of conductive material.

It is a still further object of the present invention to provide a truckbed or liner of HDPE or similar material having a conductive fabric orwebbing bonded to the upper surface of the bed or liner.

Further objects and advantage of the present invention will becomeapparent by reference to the following description of the preferred andalternate embodiments and appended drawings wherein like referencesnumbers refer to the same component, element or feature.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a pickup truck having a non-metallic boxor bed incorporating the present invention;

FIG. 2 is a greatly enlarged, fragmentary, sectional view of a truck bedaccording to the present invention taken along line 2--2 of FIG. 1;

FIG. 3 is a greatly enlarged, fragmentary, sectional view of a truck bedaccording to a first alternate embodiment of the present invention takenalong line 2--2 of FIG. 1;

FIG. 4 is a perspective view of a pickup truck and conventional metalbox or bed having a non-metallic bed liner according to the secondalternate embodiment of the present invention;

FIG. 5 is a greatly enlarged, fragmentary, sectional view of a bed lineraccording to the second alternate embodiment of the invention takenalong line 5--5 of FIG. 4;

FIG. 6 is a greatly enlarged, fragmentary, sectional view of a bed lineraccording to a third alternate embodiment of the present invention takenalong line 5--5 of FIG. 4;

FIG. 7 is an enlarged, fragmentary, top plan view of a fourth alternateembodiment bed or bed liner according to the present invention; and

FIG. 8 is a greatly enlarged, fragmentary, sectional view of a fourthalternate embodiment bed or bed liner according to the present inventiontaken along line 8--8 of FIG. 7.

DESCRIPTION OF THE PREFERRED AND ALTERNATE EMBODIMENTS

Referring now to FIGS. 1 and 2, a non-metallic pickup truck bedincorporating the present invention is illustrated and designated by thereference number 10. The non-metallic bed 10 is a unitary structurepreferably molded of an engineered thermoplastic such as high densitypolyethylene (HDPE) or similar material. The bed 10 includes outersidewalls 12 which merge smoothly with opposed generally parallel innersidewalls 14. The inner sidewalls 14 are interrupted by wheel wells 16which are suitably sized and located to receive the respective rear tireand wheel assemblies 18 of a pickup truck or similar light to mediumduty cargo vehicle 20. The opposed inner sidewalls 14 merge with atransversely extending front wall 24 which may define a single panelinterconnecting and merging with the inner opposed sidewalls 14 or adouble wall panel having inner and outer panels which interconnect andmerge with respective ones of the inner sidewalls 14 and the outersidewalls 12. The pair of inner sidewalls 14 and the transverse frontwall 24 all merge with and are interconnected by a bottom panel 26. Toimprove the strength and rigidity of the bottom panel 26, it preferablydefines a plurality of corrugations 28 which extend longitudinallysubstantially its full length. A plurality of fasteners such as carriagebolts 30 or similar devices extend through the bottom panel 26 andsecure the bed 10 to transverse braces or members 32 which are, in turn,secured to a frame or undercarriage 34 of the pickup truck 20.Preferably and typically, the non-metallic bed 10 includes backup andtail light assemblies 36 which function in accordance with aconventional practice. A tailgate assembly 38 is pivotally disposedacross the open end of the pickup truck bed 10. The pickup truck orvehicle 20 also includes a conventional cab 40 and front tire and wheelassemblies 42.

Referring now to FIGS. 2 and 3, the non-metallic bed 10 and particularlya portion of the plurality of corrugations 28 of the bottom panel 26 areillustrated in cross section. In FIG. 2, the bottom panel 26 which, asnoted, is preferably fabricated of high density polyethylene (HDPE) orsimilar engineered thermoplastic material which has been extruded into asheet and then formed to the desired size and configuration includesdispersed conductive particles 44 of carbon black or similar materialwhich are shown greatly enlarged for purposes of illustration. If carbonblack, the conductive particles 44 may be like or similar to a productdesignated XC-72 manufactured by the Cabot Corporation or the productdesignated Ketjenblack EC-300 J manufactured by Akzo Nobel Chemicals,Inc. Other conductive materials such as carbon fibers or conductivemetal particulate materials such as aluminum or copper powders or flakesare also suitable.

Preferably, the conductive particles 44 of carbon black representapproximately 18% to 22% of the total weight of material. Depending uponthe choice of conductive material and substrate, however, conductiveparticles 44 in the range of 5% to 25% by weight may be utilized. When acoarser carbon black such as Cabot's XC-72 is used 18% to 22% carbonblack by weight has produced good performance. Finer carbon black suchas Akzo Nobel's Ketjenblack EC-300 J provide similar performance whenutilized at about 8% to 12% by weight. The resulting product does andshould exhibit surface resistivity of no more than 1×10⁹ ohms andpreferably less or volume resistivity of no more than 1×10⁹ohm-centimeters and preferably less.

It should be understood that higher weight percentages of conductivematerial lower both the surface and volume resistivities and vice versa.However, mixtures having conductive material above the weightpercentages stated and resistivities significantly below those stated donot appear to confer any apparent performance benefits.

In FIG. 3, a first alternate embodiment vehicle bed 50 is illustrated.The overall structure of the vehicle bed 50 is the same as the preferredembodiment bed 10 and includes the outer and inner sidewalls 12 and 14,the front wall 24 and the bottom panel 26. The first alternateembodiment vehicle bed 50 comprises, however, a composite or sandwichhaving a first, lower layer 52 of conventional HDPE or similarengineered thermoplastic material and a second or upper layer 54 of HDPEor other material similar to the first layer 52 except that it is dopedwith dispersed conductive particles 56 such as carbon black to theweight percents and electrical resistivity discussed directly above.

The first alternate vehicle bed 50 is preferably co-extruded from asuitable extruding machine (not illustrated) and then formed asnecessary into the vehicle bed 10 illustrated in FIG. 1. It will beappreciated that the first alternate embodiment truck bed 50 exhibitssubstantially the same electrical charge dissipating characteristics asthe preferred embodiment truck bed 10. However, because it is composedof a sandwich of materials to which conductive particles 56 are addedonly to the upper or second layer 54, it utilizes a smaller amount ofconductive material per vehicle bed 50. Additionally, since the firstlayer 52 does not contain additives, its strength can be optimized.

While the electrical and charge dissipating activity of the truck beds10 and 50 according to the present invention is not fully understood, itis believed that the conductive particles 44 of carbon black or othermaterial form a conductive matrix of continuous conductive pathsthroughout the vehicle beds 10 and 50 and thereby disperse what wouldotherwise be isolated areas of electrical charge in a bed or bed liner.Through such dispersal, electric charges dissipate into the atmosphereover all or a significant portion of the surface area of the beds 10 and50 and thus are harmlessly drained off. While conductive particles 44 ofcarbon black have been found the most suitable additive or doping agentfrom the standpoint of weight, color and expense, other materials suchas carbon fibers or conductive metals such as aluminum, copper powder orflakes, as noted above, or other conductive particulate materialsachieve this same function and goal. Thus these materials as well asother analogously functioning conductive materials and metals are deemedto be within the scope of this invention.

Referring now to FIGS. 4 and 5, a second alternate embodiment of theinvention is illustrated. The present invention may also be utilized ina bed liner. A conventional pickup truck 60 includes a cab 62 and fronttire and wheel assemblies 64. The conventional pickup truck 60illustrated includes a conventional metal box or bed 66 having formedsteel sidewalls 68. The sidewalls 68 merge with a transversely extendingfront wall 74 and both the sidewalls 68 and the front walls 74 mergewith a bottom panel 76 which defines the cargo receiving area of thepickup truck 60. Typically the bottom panel 76 includes longitudinalcorrugations 78. Joining portions of the inner sidewalls 72 with thebottom panel 76 are a pair of symmetrical wheel wells 82 which receivethe rear tire and wheel assemblies 84. A tailgate 86 is transverselypivoted in the rear opening of the box or bed 66 and suitable backup andtail light assemblies 88 are also mounted in the sidewalls 68 of the bed66.

Disposed in the interior of the bed 66 and having a length, width andheight complementary to the corresponding inside dimensions of the bed66 is the second alternate embodiment of the invention, a truck bedliner 90. The truck bed liner 90 includes generally vertically disposedsidewalls 92 and a front wall 94. The truck bed liner 90 may include arail 96 which rests upon the top of the sidewalls 68 of the bed 66. Theliner sidewalls 92 and the front wall 94 merge with a bottom panel 98.The sidewalls 92, the front wall 94 and the bottom panel 98 arepreferably formed as a unitary liner from a single sheet of extrudedHDPE or other thermoplastic engineered material. Wheel wells 100complementary to the wheel wells 82 of the truck bed 66 are defined bythe bed liner 90. Preferably, the bottom panel 98 of the liner 90includes a plurality of longitudinally oriented corrugations 102 whichcorrespond to the corrugations 78 in the bottom panel 76 of the box orbed 66.

Referring now to FIG. 5, it will be appreciated that the extruded,formed and corrugated material of the bed liner 90 includes particles106 of conductive material such as carbon black or other conductivematerial uniformly dispersed therethrough. As noted above, with regardto the preferred embodiment 10, conductive particles 106 of carbon blackconstitute approximately 18% to 22% by weight of the thermoplasticmaterial of the bed liner 90. Also as noted above, carbon black, carbonfibers or other conductive particulate material may be utilized in aweight percent range of from about 5% to 25%. Regardless of thematerials chosen, as stated above, it is desirable to achieve a surfaceresistivity of no more than 1×10⁹ ohms and preferably less or a volumeresistivity of no more than 1×10⁹ ohm-centimeters and preferably less.Thus, it will be appreciated that but for the physical configuration ofthe second alternate embodiment truck bed liner 90, its purpose andbenefit as well as material constituents may be the same.

Referring now to FIGS. 4 and 6, a third alternate embodiment 110 of theinvention which is similar to the first alternate embodiment vehicle bed50 is illustrated. It is, however, a bed liner rather than a truck bed.As such, it includes the sidewalls 92, the front wall 94 and the bottompanel 98. It may include the rail 96. The third alternate embodiment bedliner 110 is a composite or sandwich construction having a first, lowerlayer 112 of HDPE or similar engineered thermoplastic material and asecond or upper layer 114 of HDPE or other material similar to the firstlayer 112 except that it includes or is doped with dispersed conductiveparticles 116 such as carbon black or other above described material tothe above described weight percents and resistivities.

The composite third alternate embodiment bed liner 110 is preferablyco-extruded from a suitable extruding machine (not illustrated) and thenformed as necessary to conform to a pickup truck bed such as the metalbox or bed 66 illustrated in FIG. 4. It will be appreciated that withthe upper conductive layer 114 of the third alternate embodiment truckbed liner 110 exhibits substantially the same electrical chargedissipating characteristics as the other embodiments discussed above,especially the first alternate embodiment vehicle bed 50. However,because it is composed of a sandwich of materials to which conductiveparticles 116 such as carbon black are added only to the upper or secondlayer 114, both layers 112 and 114 can be performance optimized. Thatis, the necessary electrical conductivity is achieved by the upper layer114 while the lower layer 112 provides optimum strength.

Referring now to FIGS. 7 and 8, a fourth alternate embodiment bed or bedliner according to the present invention is illustrated and designatedby the reference numeral 120. The fourth alternate embodiment bed 120may be either a bed 10 such as illustrated in FIG. 1 or a bed liner 90such as illustrated in FIG. 4. As such, the fourth alternate embodimentbed or bed liner 120 includes sidewalls and front wall and includes abottom panel 122 having corrugations 124 which improve the rigidity andstrength of the bottom panel 122 and may also correspond and conform tocorrugations 78 in a truck bed bottom panel such as illustrated in FIG.5. The fourth alternate embodiment bed or bed liner 120 is preferablyfabricated of high density polyethylene or other engineeredthermoplastic material such as described above. Upon the surface of thebottom panel 122 and preferably autogenously bonded thereto is a meshfabric 126 which defines generally rectangular or diamond shapedinterstices 128. The mesh fabric 126 is preferably a similar compositionpolyethylene, polyolefin elastomer or other engineered thermoplasticmaterial as described above with regard to the other embodiments orpolypropylene. The material of the mesh fabric 126 is doped or mixedwith between 5% or 25% by weight of a conductive material 130 such ascarbon black or carbon fibers or other materials described above.Conductive material 130 in the range of 18% to 22% has been foundpreferable.

It will be appreciated that the mesh fabric 126 including the conductivematerial 130 thus also provides a conductive medium through whichelectrical charges which may be developed in the bed or bed liner 120are dissipated into the atmosphere. The mesh fabric 126 has been foundparticularly efficient in this regard due to the large surface areaversus volume ratio of the mesh fabric 126 and thus the large surfacearea versus conductive material 130 ratio.

Fabrication of the fourth alternate embodiment bed or bed liner 120 andparticularly securement of the mesh fabric 126 to the bottom panel 122is preferably achieved after a flat panel is extruded from an extrudingmachine (not illustrated) but before it has cooled. At this time, themesh 126 containing the conductive material 130 is placed upon thesurface of the extruded panel after it has been flame treated but beforeit is vacuum formed into the bed or bed liner 120. Through the vacuumforming operation, the filaments of the mesh fabric 126 will be pressedor pushed into the upper surface of the bottom panel 122 of the bed orbed liner 120 such that they are both intimately bonded and mechanicallyrestrained therein.

Electrostatic charge dissipation tests have been performed on varioussamples of thermoplastic material beds and bed liners containingconductive material in accordance with MIL Spec. MIL-B81705-B. Theconductive material present in all the samples is Cabot CorporationXC-72 carbon black. Samples A and B are corrugated HDPE according to thepreferred and the first, second or third alternate embodiments. Sample Cis an embossed bed or bed liner and Sample D is a bed or bed lineraccording to the fourth alternate embodiment. The surface resistivitiesachieved are the result of many variables, the most significant ofwhich, from the standpoint of the conductive material, is its particlesize. Thus, a carbon black finer than Cabot's XC-72 carbon black such asAkzo Nobel's Ketjenblack EC-300 J may be used in amounts reduced by asmuch as 50% and perhaps more so that good results are achieved with aslittle as approximately 10% carbon black. Such finer carbon blacks andother conductive materials are, however, typically more expensive andthus it represents simply an alternative rather than a directed choice.The surface resistivities appearing below in Table I are the averagevalues of three separate measurements made on each sample.

                  TABLE I    ______________________________________              CARBON BLACK SURFACE RESISTIVITY    SAMPLE    (per cent)   (ohms/sq.)    ______________________________________    A         19           4.17 × 10.sup.7    B         19           6.55 × 10.sup.7    C         19           6.17 × 10.sup.8    D         19           6.67 × 10.sup.8    ______________________________________

It will be appreciated that while the invention has been described as apickup truck box or bed liner in the various embodiments, the inventionis equally suited for and intended for use in other cargo hauling andliner applications such as in minivans, sport utility vehicles and cargovans. These various applications are all consistent with and envisionedby the inventor inasmuch as the primary purpose and goal of theinvention is to provide a bed or liner having electrical chargedissipating characteristics.

The foregoing disclosure is the best mode devised by the inventor forpracticing this invention. It is apparent, however, that apparatusincorporating modifications and variations will be obvious to oneskilled in the art of cargo beds and bed liners. Inasmuch as theforegoing disclosure presents the best mode contemplated by the inventorfor carrying out the invention and is intended to enable any personskilled in the pertinent art to practice this invention, it should notbe construed to be limited thereby but should be construed to includesuch aforementioned obvious variations and be limited only by the spiritand scope of the following claims.

I claim:
 1. A receptacle for a cargo vehicle comprising, in combination,a pair of sidewalls, a front wall, a bottom panel joining said sidewalls and said front wall, and said receptacle made of a thermoplastic material, at least a portion of said thermoplastic material including dispersed electrically conductive material.
 2. The receptacle for a cargo vehicle of claim 1 wherein said receptacle is a vehicle bed.
 3. The receptacle for a cargo vehicle of claim 1 wherein said receptacle is a bed liner.
 4. The receptacle for a cargo vehicle of claim 1 wherein said receptacle is made of high density polyethylene.
 5. The receptacle for a cargo vehicle of claim 1 wherein said conductive material is carbon black.
 6. The receptacle for a cargo vehicle of claim 1 wherein said thermoplastic material is a composite having a lower layer of thermoplastic material and an upper layer of thermoplastic material containing said dispersed electrically conductive material.
 7. The receptacle for a cargo vehicle of claim 1 further including a mesh secured to said bottom panel and wherein said electrically conductive material is dispersed in said mesh.
 8. The receptacle for a cargo vehicle of claim 1 wherein said thermoplastic material including dispersed electrically conductive material exhibits a surface resistivity of 1×10⁹ ohms or less.
 9. The receptacle for a cargo vehicle of claim 1 wherein said thermoplastic material including dispersed electrically conductive material exhibits a volume resistivity of 1×10⁹ ohm-centimeters or less.
 10. A cargo bed for a pickup truck and the like comprising, in combination,a pair of opposed sidewalls, a front wall having ends merging with said sidewalls, and a bottom panel merging with said front wall and said pair of sidewalls, said bed made of a thermoplastic material containing dispersed electrically conductive material.
 11. The cargo bed for a pickup truck and the like of claim 10 wherein said receptacle is made of high density polyethylene.
 12. The cargo bed for a pickup truck and the like of claim 10 wherein said electrically conductive materials is carbon black.
 13. The cargo bed for a pickup truck and the like of claim 10 wherein said thermoplastic material is a composite having a lower layer of thermoplastic material and an upper layer of thermoplastic material and electrically conductive material.
 14. The cargo bed for a pickup truck and the like of claim 10 wherein said conductive particles form a conductive matrix in said thermoplastic material.
 15. The cargo bed for a pickup truck and the like of claim 10 wherein said thermoplastic material containing said electrically conductive material exhibits a surface resistivity of 1×10⁹ ohms or less.
 16. The cargo bed for a pickup truck and the like of claim 10 wherein said thermoplastic material containing said electrically conductive material exhibits a volume resistivity of 1×10⁹ ohm-centimeters or less.
 17. A liner for a cargo vehicle comprising, in combination,a pair of spaced apart sidewalls, a bottom panel joining said sidewalls, and said sidewalls and said bottom panel made of thermoplastic material and having at least a portion of said thermoplastic material including dispersed conductive particles.
 18. The liner for a cargo vehicle claim 17 wherein said thermoplastic material is high density polyethylene.
 19. The liner for a cargo vehicle of claim 17 wherein said conductive particles are carbon black.
 20. The liner for a cargo vehicle of claim 17 further including a front wall merging with said sidewalls and said bottom panel.
 21. The liner for a cargo vehicle of claim 17 wherein said thermoplastic material including dispensed conductive particles exhibits a surface resistivity of 1×10⁹ ohms or less.
 22. The liner for a cargo vehicle of claim 17 wherein said thermoplastic material including dispersed conductive particles exhibits a volume resistivity of 1×10⁹ ohm-centimeters or less.
 23. The liner for a cargo vehicle of claim 17 further including a mesh fabric disposed on said bottom panel, said mesh fabric including said conductive particles.
 24. A cargo receiving device for a vehicle, comprising, in combination,a panel adapted for horizontal disposition and receipt of cargo, at least two sidewalls extending from said panel, said panel made of a doped thermoplastic material having a surface resistivity of less than 1×10⁹ ohms.
 25. The cargo receiving device of claim 24 wherein said doped thermoplastic material includes conductive particles.
 26. The cargo receiving device of claim 25 wherein said conductive particles are carbon black.
 27. The cargo receiving device of claim 24 further including a front wall merging with said two sidewalls.
 28. The cargo receiving device of claim 24 wherein said doped thermoplastic is HDPE and includes carbon black in the range of from 5 to 25 weight percent.
 29. The cargo receiving device of claim 24 further including a front wall merging with said sidewalls and said panel, sidewalls and front wall define a pickup truck bed.
 30. The cargo receiving device of claim 24 further including a front wall merging with said sidewalls and said panel, sidewalls and front wall define a pickup truck bed liner.
 31. The cargo receiving device of claim 24 wherein said panel exhibits volume resistivity of less than 1×10⁹ ohm-centimeters. 